1. Field of the Invention
The present invention relates to a picture tube with a deflection yoke mounted thereon and more particularly to apparatus for mounting said deflection yoke.
2. Description of the Prior Art
The deflection yoke for a picture tube is mounted on the tube neck and rests against the funnel of the picture tube. After the deflection yoke is mounted on the picture tube, it must be adjusted precisely in relation to the latter, so that a perfect picture is obtained. Subsequently, the deflection yoke must be attached to the picture tube so that it can no longer shift. When the deflection yoke is mounted on the picture tube, the temperature and the pressure on the picture tube must not be too high, because this can result in damage to the picture tube.
As disclosed, for example, in DE-OS No. 24 08 673, the deflection yoke can be mounted on the picture tube either mechanically or by adhesive bonding. Thus, the deflection yoke can, for example, be fastened to the picture tube by a clamp which can be tightened by means of a screw. If the screw is loosened, the deflection yoke can be moved on the tube neck, and can be fixed after adjustment by tightening the screw. However, the pressure exerted must not be too high so as to avoid cracking of the tube neck.
If the deflection yoke is fixed to the tube neck by adhesive bonding, a suitable adhesive has to be introduced between the deflection yoke and the picture tube. This is difficult and often requires special channels to introduce the adhesive. A cold-setting adhesive has the advantage that the temperature effect on the picture tube is small; the disadvantage is, however, that on the one hand, the adjusting operation must be completed before the adhesive sets, while on the other hand, the deflection yoke must be held in position until the adhesive sets.
If an adhesive is used which softens with the application of heat, the softening temperature must not be too high, so that an unfavorable impact on the picture tube is avoided during initial application. On the other hand, th picture tube must not be heated during operation to the softening temperature or the deflection yoke may shift.
Since evidently the deflection yoke cannot be mounted satisfactorily on the picture tube by any of the above means, DE-OS No. 24 08 673 proposes to provide the funnel of the picture tube with ribs or rough spots to prevent the adjusted deflection yoke from being shifted. However, this requires that the body of the picture tube be designed or treated in a special manner.
In accordance with DE-AS No. 23 42 052, individual strips of thermoplastic material joining the deflection yoke and the picture tube are to be cemented in the longitudinal direction between the two parts. To this end, a hot-setting adhesive having a melting temperature of about 150.degree. C. is used. When the hot-setting adhesive is introduced, the picture tube must be kept at a temperature of 50.degree. C. Furthermore, the deflection yoke must have suitable channels into which the hot-setting adhesive can be introduced.
It is known from DE-OS No. 24 51 288 to mount a deflection yoke on a picture tube by first attaching a ring with four hollow pins to the funnel of the picture tube by means of an adhesive. On its circumference, the deflection yoke has lugs pointing radially outwardly which are inserted into outwardly projecting recesses of a second plastic ring. Both parts together are then placed on the pins of the first ring and are joined together by introducing an adhesive. In this embodiment, several parts of complex shapes are required which must be joined together.